Bioługowanie metali ciężkich z odpadów pogalwanicznych przy neutralnym pH środowiska, w obecności bakterii produkujących biosurfaktanty

Precipitates and sludges from the galvanic industry are one of the sources of the environment contamination with heavy metals. Therefore, the investigations are carried out in order to developer the effective method of metals elimination from these wastes. The promising results are obtained in case of the application of microbial leaching. Up to now results concerned mainly the metals bioleaching in acidic environment. In this research work the possibility of heavy metals removal from galvanic wastes using the culture of sulphur oxidizing bacteria (pH 2-4) and a mixed culture of both sulphur oxidizing bacteria and biosurfactant producing bacteria (pH 6.5-8) was examined. It allowed to compare the process effectiveness in acidic and neutral environment. The cultures were prepared based on the activated sludge from the municipal wastewater treatment plant. The presence of sulphur oxidizing bacteria Acidithiobacillus ferrooxidans was confirmed using the PCR method. Bacillus subtilis and B. cereus strains were applied as biosurfactant producers. Three galvanic wastes, different in grain size, water content and heavy metal concentration, were bioleached. The research revealed that the metal release from galvanic wastes was more effective in presence of biosurfactant, especially in case of copper, but also for cadmium and chromium. The process effectiveness in acidic condition was comparatively lower. Zinc was the only metal that was bioleached faster in acidic environment, with similar final metal removal after 25 days of the process. The maximum values of metals elimination in the presence of biosurfactant depended on the bioleached waste type and were: 7.1-100% for copper, 3.7-50.3% for zinc, 30-50.5% for chromium, 34.1-71.9% for cadmium. The effectiveness of the nickel and lead removal was lower than 5%. The prolongation of the bioleaching period up to 40 days in case of waste C (the less susceptible to the bioleaching) resulted in elimination of 67.9% of Cu, 34.7% of Zn, 100% of Cr and 39.1% of Pb, while the effectiveness of nickel removal was still very low.